guidelines for life cycle assessment of carbon capture and utilisation · 2020. 5. 7. ·...

LCA4CCU

Guidelines for Life Cycle Assessment of Carbon Capture and Utilisation

DG ENER March 2020 Document reference: LCA4CCU001

DG ENER

LCA4CCU Document reference: LCA4CCU001 March 2020

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Process

Name Date

Prepared by Andrea Ramirez Ramirez Aïcha El Khamlichi Georg Markowz Nils Rettenmaier Martin Baitz Gerfried Jungmeier Tom Bradley

2020-03-29

Reviewed by Andrea Ramirez Ramirez Aïcha El Khamlichi Georg Markowz Nils Rettenmaier Martin Baitz Gerfried Jungmeier Tom Bradley

2020-03-29

Approved by Andrea Ramirez Ramirez Aïcha El Khamlichi Georg Markowz Nils Rettenmaier Martin Baitz Gerfried Jungmeier Tom Bradley

2020-03-29

Version History

Version Date Author Reason for Issue

1.0 2020-03-29

Andrea Ramirez Ramirez Aïcha El Khamlichi Georg Markowz Nils Rettenmaier Martin Baitz Gerfried Jungmeier Tom Bradley

Final version for publication

This report was initiated and financially supported by the European Commission Directorate-General for Energy. The authors are solely responsible for the content of this report, and it does not represent the opinion of the European Commission.

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Contents

1 Executive summary 1

2 Introduction 5

2.1 Background 5

2.2 Context 7

2.3 Approach 8

2.4 Normative references and references to LCA guidelines 8

3 Terms and definitions 9

3.1 Definition of CCU 9

3.2 The CCU system 9

3.3 Sources of CO2 11

4 ISO alignment 13

4.1 Goal and scope definition 13

4.2 Life Cycle Inventory analysis (LCI) 14

4.3 Life Cycle Impact Assessment (LCIA) 14

4.4 Life Cycle interpretation 14

5 Goal definition 15

5.1 Goal of the LCA study 15

5.2 General requirements (for any LCA study) 15

5.3 Specific requirements for LCA for CCU studies 15

5.4 Summary and key messages 17

6 Scope definition 18

6.1 Scope of the LCA study 18

6.2 General requirements (for any LCA study) 18

6.3 Specific requirements for LCA for CCU studies 19

6.3.1 Product system to be studied 19

6.3.2 Function, functional unit and reference flow 19

6.3.3 System boundaries 20

6.3.4 Allocation procedures / Approaches for solving multifunctionality 22

6.3.5 LCIA methodology and types of impacts 22

6.4 Summary and key messages 22

7 Description of CCU system 24

7.1 Introduction 24

7.2 Main Processes 24

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7.3 Key information and parameters of main processes 25

7.4 CO2 sources 27

7.5 Carbon flows to/from atmosphere and CO2 pool in atmosphere 28

7.6 Comparison to reference system 31

7.7 Summary - key messages 32

8 Data and model aspects in life cycle inventory and its related responsibilities 33

8.1 Responsibilities 33

8.2 Adequate model and data 33

8.3 Overview and definition of data 35

8.4 Potential pitfalls and sources of error in CCU 36

8.5 Considerations concerning gap closing 37

8.6 LCA Data collection, handling and provision 37

8.7 Conclusion 38

9 Feedstock- and energy-related aspects 39

9.1 Introduction 39

9.2 Credits and burden for CO2 39

9.2.1 CCU plant is added to an existing CO2 emitting plant without further interaction 39

9.2.2 Existing CO2 emitting plant is operated differently after installation of CCU plant 41

9.2.3 CO2 emitting and CCU plants are built together 42

9.3 Electricity for direct use within a CCU plant and/or for production of H2 42

9.3.1 Preliminary remarks: Electricity - increasingly relevant but also challenging in LCA 42

9.3.2 Electricity from additional renewable power plants via Power Purchase Agreements (PPAs) 43

9.3.3 Electricity from specific conventional power plants by defined contracts 45

9.3.4 Electricity from the grid 45

9.3.5 Concluding remarks 46

9.4 Selected other sources than renewable electricity for low-carbon intensity H2 47

9.4.1 H2 from Natural Gas via SMR+CCS or via Pyrolysis 47

9.4.2 H2 as co-product from industrial processes 47

9.5 Use of otherwise lost heat 48

10 Impact Categories 50

10.1 General 50

10.2 Impact Categories to Consider 50

10.3 Future Impact Analysis 51

10.4 Water Use Issues 51

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10.5 Climate Change Specific Issues 52

10.5.1 GWP20 52

10.5.2 Delayed Emissions 52

10.5.3 Ensuring harmonisation within GWP impacts 53

10.6 Recommendations 54

11 Uncertainty analysis 55

11.1 Diagnostic vs Prognostic Uncertainty Analysis 57

11.2 What-will (prognostic) assessments 58

11.3 Aim for transparency 58

11.4 Tools and approaches 59

11.5 Summary of Recommendations 62

12 Conclusions 63

13 Outlook 65

14 Abbreviations 67

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Figures

Figure 1: Global GHG emissions versus production volumes of top 18 large-volume chemicals, 2010 (Source: IEA, ICCA & DECHEMA) ................................................................................................................... 5

Figure 2: Simple classification of CO2 uses (Source: IEA) ........................................................................... 10

Figure 3: Example of key product chain ...................................................................................................... 10

Figure 4: CO2 sources: from concentrated to diluted CO2 .......................................................................... 11

Figure 5: The four phases of LCA ................................................................................................................ 13

Figure 6: Decision tree to identify the goal of the LCA ............................................................................... 16

Figure 7: System boundary for fossil and biogenic CO2: cradle-to-grave ................................................... 21

Figure 8: System boundary for CO2 from direct air capture (DAC): gate-to-grave ..................................... 21

Figure 9: Main processes of the CCU system .............................................................................................. 25

Figure 10: Example for continuous and flexible operation: Electrochemical conversion of CO2 to ethylene a) continuous (from grid); b) intermittent from dedicated wind power .................................................... 27

Figure 11: Scheme of Carbon flows and atmospheric CO2 pool affected by the CCU System ................... 29

Figure 12: CO2 in atmosphere affected by different types of Carbon, pools and flows ............................. 29

Figure 13: Example 1: CCU System (material) & CO2 flows ........................................................................ 30

Figure 14: Example 2: CCU System (Fuel) & CO2 flows ............................................................................... 30

Figure 15: Life Cycle System model combining “foreground data” with “fit for purpose” and actual background data ......................................................................................................................................... 34

Figure 16: Types, sources and nature of different data needed in an LCA for CCU ................................... 36

Figure 17: Three areas to gain reliable and mindful LCA results (for CCU) ................................................ 38

Figure 18: Schematic flow of CCU plant exploiting CO2 from a primary emitter which, besides providing CO2 does not change its operation ............................................................................................................. 39

Figure 19: Schematic flow of CCU plant exploiting CO2 from a primary emitter which, upon provision of CO2 changes its operation ........................................................................................................................... 41

Figure 20: Schematic setting of CCU plant exploiting heat from a separate source where the heat has not been utilised so far ...................................................................................................................................... 48

Figure 21: Horizon time of CO2 emissions from CO2 based products ......................................................... 52

Figure 22: Uncertainty over a technology development path33 ................................................................. 57

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Tables

Table 1: Potential sources of CO2 with average cost of capture ................................................................. 12

Table 2: Combination of two main aspects of the decision-context: decision orientation and kind of consequences in the background system or other systems. Source: ILCD Handbook ............................... 16

Table 3: Recommended functional units (FUs) ........................................................................................... 20

Table 4: Figures from TAR, AR4 and AR5. Note, the AR5 figures are for fossil methane, biogenic methane provides figures of 28 kgCO2eq(GWP20) and 84 kgCO2eq(GWP100) ......................................................... 53

Table 5: Example of tools and approaches currently available for uncertainty management,,, ................. 59

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1 Executive summary Carbon Capture, Utilisation and Storage (CCUS) is perceived as one of the options available to address the hardest-to-abate emissions from process industries such as iron & steel, cement and chemicals, which are heavily carbon-intensive. CCUS includes storing CO2 in geological formations (for example in a deep saline aquifer) as well as its use in processes for conversion into chemical products, building materials or fuels. The largest benefits of CCUS in literature are mostly from the geological storage (CCS), while the potential benefit of utilisation options (CCU) is still under investigation. In this report, the focus is only on the capture and use of CO2 as raw material in conversion processes, although the guidelines and principles can be applied to CO2 used in other processes.

This report aims, within the framework provided by DG Energy, to develop Life Cycle Assessment (LCA) guidelines for Carbon Capture and Utilisation. As a point of departure, CCU is defined in this report as “those technologies that use CO2 as feedstock and convert it into value-added products such as fuels, chemicals or materials”. CCU involves a number of stages, from capturing the CO2 to its conversion into carbon-containing products, further including the use of such products up to their disposal as carbon-containing waste and/or ultimately, CO2 emission, which may happen shortly after the use of the CO2-derived product (e.g., synthetic fuels) to decades (e.g., for polymers) or centuries (e.g., for mineralization products). Many of these stages demand energy, not only directly (in the capture system and the transformation processes) but also indirectly (in the synthesis of co-reactants such as hydrogen). The products will then be used in other chains.

Understanding the potential benefits or impacts on the environment, requires that not only the direct impacts from the CCU production facility are considered but also the impacts from provision of feedstock and from use and end of life of products. Furthermore, impacts (or benefits) are not restricted to those of climate change but should also include other environmental aspects (land use, water use, etc.). As a consequence, CCU’s beneficial or negative impacts should be assessed from a system perspective and with regards to how it can provide societal benefits.

The principles of LCA are already described in ISO 14040 and 14044, and so the purpose of this work is not to revise these principles. The report does not aim to replace existing standards (e.g., EN ISO 14040 and EN ISO 14044), rather it departs from the standards and existing state-of-the-art knowledge in LCA to address points that are particularly relevant for CCU. In doing so, the objective of the report is to identify and highlight the most “controversial” topics when applying LCA to CCU technologies. Whenever possible, recommendations are made for each step of an LCA: goal and scope (functional unit and system boundaries), reference systems, data and models, impact categories and uncertainty analysis. Uncertainty is not exclusive of LCAs of CCU. However, as most CCU technologies are currently at an early stage of development (e.g., lab-scale), outputs from LCAs addressing those technologies have inherently large(r) uncertainties. Therefore, a discussion on the impact of uncertainty is also part of this work.

Main recommendations:

The key strength of LCA is that the methodology can be applied to address the environmental aspects and potential environmental impacts throughout the life cycle of any good or service. Given this wealth of possibilities, it is, however, very important to precisely describe the research question to be answered. This may seem a trivial point, but a review of LCA literature on CCU concepts already indicates that this point is sometimes overlooked or forgotten throughout the study (i.e. implications of a given goal setting at the start of the study do not match the methodological choices or conclusion drawn from the study). Since the goal definition is decisive for all the other phases of the LCA, a clear initial goal definition is crucial for a correct later interpretation of the results. It is thus recommended to pay particular attention to the goal definition since it affects the results and also the comparability of LCA studies. The present guidelines are intended to cover “decision support” situations according to the ILCD Handbook; therefore

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“accounting” cases are out of scope of the present guidelines.

The present guidelines require that “cradle-to-grave” should be the default system boundary to assess the environmental impact of a CCU technology. Only in this way, meaningful conclusions regarding carbon neutrality/negativity can be drawn in an unrestricted form. Other system boundaries are discouraged (“cradle-to-gate”) or even strongly discouraged (“gate-to-gate”); however, they may be chosen on the condition that a justification is provided and that the conclusions drawn from the study do not (explicitly or implicitly) expand or cover issues that can only be done with larger system boundaries.

The selection of the reference system plays an important role for understanding the potential environmental benefits (or pitfalls) of a CCU option. Because many CCU options are currently at low TRL level, the selection of a proper reference system remains challenging. In this guideline, we recommend that more than one scenario shall be explored (such scenarios can include various reference systems, various backgrounds, etc.). Selecting only a single future scenario (e.g., novel technology vs today's technology) runs the risk of over- (or under-)stating uncertainties that are identified as well as producing blind spots. When defining the scenarios, care should be taken that they are both temporally and spatially consistent.

Regarding the impact categories, in this guideline, we use CML Impact Categories, but other categories may be used. It shall, however, be clear and explicitly reported which impact categories are used, including the name of methodology, version, and date released. Because one of the key values added by LCA is the potential to identify trade-offs among categories, here we recommend that all impact category types should be used, and if not, justification shall be given. Although the motivation of CCU often lies in climate change and therefore many studies focus only on indicators related to greenhouse gases (e.g., Global Warming Potential), it is important for proper decision making to identify potential areas where trade-offs can occur as a consequence of CCU implementation. Furthermore, when looking at GWP, to understand short- and long-term impacts, it is recommended that both GWP20 and GWP100 should be used. Finally, in this guideline we recommend that delayed emissions less than 500 years shall be treated as emitted at year zero, emissions delayed greater than 500 years (to a reasonable level of certainty) should be ignored.

In this guideline, we further recommend that system expansion shall be used. Sometimes, however, allocation procedures are required, and as such allocation of CO2 is one of the most relevant topics in LCA for CCU and also a potential pitfall. Very strict compliance to guidelines is essential along with very clear communication of selected procedures at distinct places within the LCA and an assessment of the impact of allocation choices as part of the uncertainty analysis. Particular care should be taken to avoid that inadvertently emissions 'disappear' from the system, for instance, by assuming that emissions are accounted for by a party that is outside the system boundaries. In this guideline, we depart from a precautionary principle, which says that if the origin of the CO2 to be used in the CCU options is not known or if the origin is known but there is no agreement on who has the burden of the emissions due to CO2 capture and transport, the CCU system shall incorporate those into its system boundaries. Note that unless there is specific information about the source of the CO2, it shall not be assumed that the flow is of non-fossil origin (i.e. CO2 is considered of fossil origin unless information is provided which justifies to consider it biogenic or atmospheric).

Regarding impacts of (background) data, electricity tends to be much more relevant for most CCU applications than for others. Refinement compared to standard LCA is strongly recommended to improve quality of LCA for CCU, especially, it is important to consider impact of flexible operation on plant model and foreground data (e.g., if the system is assumed to use only intermittent renewables or is considered to provide an energy storage service to the grid); to further apply additionality and marginal electricity concepts, time-resolved data and to consider location of CCU plant and related potential grid restrictions.

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Finally, uncertainty analysis remains an indispensable part of LCA and even more so for LCA of technologies that are not yet commercial. We recommend that whenever possible, a combination of quantitative and qualitative uncertainty methods should be used as they provide specific insights into the types of uncertainties and their significance in the analysis and that as a minimum, any LCA of CCU should provide a thorough report of uncertainties (in data, models, allocation choices, etc.) regardless of whether they can be (quantitatively) measured.

To conclude, no general gaps in LCA methodology were identified in application to CCU. Instead, it showed that also for CCU, LCA is THE tool of choice for assessment of environmental impacts of technologies. Nevertheless, some topics are recommended for future work in the context of LCA for CCU to accelerate the adoption of recommendations made within this report and to improve familiarity within the LCA community:

● To develop and provide examples of LCA for selected CCU cases as best practice references. In this context, examples with high relevance, either because of the absolute amount of CO2 emitted by the respective kind of source or because of the product market size (e.g., fuels, olefins, methanol, BTX aromatics, urea) could be of special interest.

● To validate applicability of the guidelines of this report also on example cases of other, chemical energy containing gaseous components such as hydrogen or carbon monoxide which may come along with a CO2 containing waste gas (as for example in steel mill waste gases) and - if meaningful or necessary - to expand the scope and/or add specific recommendations to the guidelines.

● To elaborate higher frequencies of background data updates and validations. This includes especially the mandatory use of most recent IPCC figures for any LCA for CCU.

● To support well defined and accepted scenarios for selected reference systems as the background system will change so fast in the coming years, though at relatively high uncertainty, to enable efficient execution of LCA as well as comparability of LCA studies by practitioners. Those reference systems should include the power system in general (including share and location of renewables, kind of renewables, level of grid development, time-dependent resolution of power production and general demand) as well as state-of-the-art for selected key industrial processes, e.g., for steel, glass and cement making and production of selected base chemicals for selected points in time, e.g., by 2030, 2040 and 2050.

● To develop and to make available background data for carbon capture technologies due to its relevance for LCA for CCU. Improvement regarding both quality and quantity of data in this area is strongly encouraged.

● Due to the relatively high number of low TRL cases among CCU technologies, it is recommended to generally foster experience with treatment of uncertainty within LCA. Uncertainty, in general, is not a specific issue of CCU technologies. Yet, its relevance is in tendency higher in the area of CCU. The common level of understanding and experience could be improved by dedicated research as well as a general stronger emphasis in future LCA.

● To develop LCI databases for CCU systems in order to support practitioners in the development analysis of CCU.

The focus of this work has been on LCA aiming to support decision making. In the case of LCA aiming for accounting it may be desirable to apply allocation instead of system expansion which could cause different results. There is no simple rule available today how to avoid such potential mismatches. It remains in the responsibility of the LCA practitioner to be aware of such differences and to consider them adequately in the interpretation of the results. Additionally, it might be useful to elaborate on selected examples of how such mismatches could be avoided or at least to provide a guideline on how to deal with it.

Beyond these recommendations, there are topics which fall out of the direct scope of LCA for CCU and/or require inclusion of additional expertise, nevertheless, it is anticipated that proper solutions would be of high value to ensure good fit between real operation of CCU plants and results from their respective

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models within an LCA study. For example, it would be meaningful to provide operators of CCU plants which are designed and intended to operate only in selected situations for marginal grid mix (e.g., at sufficiently low carbon footprint), with an online tool which enables them to predict within reasonable certainty the marginal mix over a reasonable period of time in the future (e.g., up to a day ahead). Also, it is to be clarified how - in the context of additionality - renewable power plants shall be treated which fall out of the regime of any public funding scheme but which will need some investment in refurbishment prior to continued use. Neither treatment as additional renewable power nor as already fully existing renewable power installation seems adequate. Further topics may come up within the context of future application of LCA for CCU.

Finally, especially in the context of meso-/macro-level decision support by LCA and furthermore in cases which strongly rely on use of renewable electricity, it would be very meaningful to develop guidelines for how to assess the impacts of a large scale deployment of the respective CCU technology. Specifically, it would be very useful if information such as total renewable electricity demand, required transmission grid capacities, area demand for renewable power generation and transmission lines, impact of CCU plants and additional renewable power installations on availability of renewable power for other applications would be consistently developed and analysed in order to reflect future potential competition for renewable electricity, land use and grid capacity with other sectors.

Further issues which fall out of the scope of LCA for CCU specifically, but are important, are the issues highlighted in terms of the inconsistencies over the method used for climate change impacts, both the version issue (TAR, AR4, or AR5) and also the application of these methods. There needs to be greater work between LCA practitioners and the IPCC to resolve this issue.

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2 Introduction

2.1 Background

Today, more than 220 Mt carbon dioxide (CO2) are used globally each year1. The largest consumer is the fertiliser industry, which consumes 100 Mt CO2 per year for urea manufacturing (of which the vast majority is produced upstream by natural gas steam reforming), followed by the oil sector at nearly 80 Mt CO2 for CO2 Enhanced Oil Recovery (CO2-EOR). Other commercial applications include food and beverage production, metal fabrication, cooling, and fire suppression; CO2 is also used in greenhouses to stimulate plant growth.

A potential benefit of Carbon Capture and Utilisation (CCU) is the substitution of fossil-based products. In the chemical industry, greenhouse gas (GHG) emissions of catalytic chemical processes are dominated by the top large-volume products2 (see Figure 1). The substitution of these fossil-based products could increase the market potential of CCU. The benefits in terms of GHG emissions will, however, depend on the carbon footprint of the energy used for the CCU process, the carbon emitted in the upstream and downstream processes and the lifetime of the product it replaces.

Figure 1: Global GHG emissions versus production volumes of top 18 large-volume chemicals, 2010 (Source: IEA, ICCA & DECHEMA3)

CCUS, Carbon Capture, Utilisation and Storage, is perceived as one of the options available to address the hardest-to-abate emissions from process industries such as iron & steel, cement and chemical industries, which are heavily carbon-intensive. Globally, industrial carbon dioxide (CO2) emissions have increased by

1 Transforming Industry through CCUS, IEA, May 2019

2 Technology Roadmap “Energy and GHG reductions in the chemical industry via catalytic processes”, IEA, ICCA

& DECHEMA, 2013 3 Ibid.

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70% between 1990 and 20174, making the industry the second-largest source of CO2 emissions. With one-quarter of industrial emissions related to non-combustion process emissions such as chemical reactions, CCUS is considered by some as unavoidable and a cost-effective option for the future to reduce emissions from industrial processes. CCUS includes CO2 geologically stored (for example in a deep saline aquifer) or used in processes for conversion into chemical products, building materials or fuels. The largest benefits of CCUS in literature are mostly from the geological storage (CCS), while the potential benefit of utilisation options (CCU) is still under investigation. In this report, the focus is only on the capture and use of CO2 as raw material in conversion processes, although the guidelines and principles can be applied to CO2 used in other processes.

Carbon dioxide, CO2, is a molecule at a very low energy level and with high thermodynamic stability. Therefore, it typically needs considerable energy input for its conversion into a product. Other raw materials could be used as co-reactant for CO2 (e.g. hydrogen) to enable the conversion at milder (temperature, pressure) conditions. Such co-reactants however also require energy and materials for their production. Therefore, it is crucial to assess the life cycle impact of CO2 capture and conversion processes to identify the potential benefits and trade-offs of these new technologies.

This report aims, within the framework provided by DG Energy, to develop Life Cycle Assessment (LCA) guidelines for Carbon Capture and Utilisation (CCU). As a point of departure, CCU is defined in this report as “those technologies that use CO2 as feedstock and convert it into value-added products such as fuels, chemicals or materials”.

CCU involves a number of stages, from capturing the CO2 to its conversion into carbon-containing products, from the use of such products to their disposal as carbon-containing waste, and ultimately, CO2 re-emission, which may happen shortly after CO2 conversion (e.g. synthetic fuels) to decades (e.g. for polymers) or centuries (e.g. mineralization products). All these stages demand energy, not only directly (in the capture system and the transformation processes) but also indirectly (in the synthesis of co-reactants such as hydrogen). The products will then be used in other chains. Understanding the potential benefits or impacts onto the environment, requires that not only the direct impacts from the CCU production facility are taken into consideration but also the impacts due to feedstock requirements and end of life. Furthermore, impacts (or benefits) are not restricted to those of climate change but should also include other environmental aspects (land use, water use, etc.). As a consequence, CCU’s beneficial or negative impacts should be assessed from a system perspective and with regards to how it can provide societal benefits.

Various studies have attempted to identify which societal services CCU could provide. Among the most named ones are:

● Long-term energy storage into chemical bonds (from intermittent renewable energy); ● CO2 as an abundant feedstock that could increase feedstock security of industrial sectors; ● Improving the sustainability of industrial processes (green chemistry), ● A potential pathway to implement circularity in industrial systems.

This approach, based on societal services, is new and could lead to misinterpretations when applying a full LCA for a CCU technology. It is why, here, a systematic discussion of aspects for the application of LCA specifically for CCU technologies is described.

The principles of LCA are already described in ISO 14040 and 14044, and so the purpose of this work is not to revise these principles. The objective is to identify and highlight the most “controversial” topics when applying LCA to CCU technologies. When possible, recommendations are made for each step of an LCA: goal and scope (functional unit and system boundaries), reference systems, data and models, impact categories and uncertainty analysis. Uncertainty is not exclusive of LCAs of CCU. However, as most CCU

4 Exploring Clean Energy Pathways - The Role of CO2 Storage, IEA, July 2019

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technologies are currently at an early stage of development (e.g. lab scale), outputs from LCAs addressing those technologies have inherently large uncertainties. Therefore a discussion on the impact of uncertainty is also part of this work.

This document focuses on how to handle the specificities of LCA for CCU. It provides additional requirements and guidelines for CCU products:

● Chapter 3 introduces the terms used in the report and gives a definition of CCU technologies as a framework for this study.

● Chapters 4 through 8 follow the different phases of LCA and provide guidance specifically for LCA for CCU.

● Chapter 9 focuses on the description of the studied system, i.e. CCU system (what information should be used for the assessment) and the reference systems with the methodology for the choice of technology

● Chapter 10 presents key elements on data and models aspects. Also, impact categories are discussed in the chapter.

● Chapter 11 provides technical information on selected feedstock- and energy-related aspects. The assumptions made by the practitioner on these elements may have major impacts on the result of the assessment.

● Chapter 12 provides details regarding the selection of impact categories. ● Chapter 13 carries out an analysis of the impact of uncertainty on the result of the assessment.

Even if uncertainty analysis is not specific to CCU technologies, it is a main point in the interpretation of the results of LCA.

● Chapter 14, the last one, summarises the main recommendations and gives an outlook on potential next steps of this work.

2.2 Context

This document is a set of guidelines for the Life Cycle Assessment (LCA) of Carbon Capture and Utilisation (CCU), to identify and, when possible, address some of the key challenges when developing LCA of CCU.

The work departed from a review of the literature regarding LCA methodology and the application to CCU. Although a significant amount of scientific work on LCA for CCU, especially on case studies, is increasingly available, there is still a lower level of experience and expertise in case of LCA for CCU and several challenges exist in selecting adequate assumptions and methods because specific boundary conditions in CCU chains often have a higher impact than in other areas of LCA application.

The general description of Life Cycle Assessment is defined in EN ISO 14040:2006. This report is based on the standards EN ISO 14040 and EN ISO 14044.

Based on the above, in summary, our points of departure are:

● This document was developed from a purely scientific perspective, free from policy and economic considerations, in order to cover all possible routes and products.

● The document is built on existing and undisputed state of the art in LCA.

● The document should support the identification of potential pitfalls and limitations within LCA

for CCU and prioritize such issues.

● The document aims to provide first recommendations to overcome key issues. The LCA

recommendations should be applicable by practitioners.

● The document should highlight where LCA for CCU differs from other cases of LCA, we are not

recreating all of LCA.

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● As a key principle of LCA, transparency is required, whilst respecting intellectual property

protection by partners.

2.3 Approach

This document has been produced by a group of 7 experts from different areas of expertise but with a track record on LCA. This document was created through an extensive review of the literature regarding LCA methodology and its application to CCU. The first step was to identify the main pitfalls and limitations within LCA for CCU and prioritize such issues. A workshop gathering LCA experts was organised in May 2019 to present and discuss the identified pitfalls and limitations. Feedback from the participants was also requested. Then, the main work focused on producing recommendations to overcome the identified issues. A second workshop gathering a larger number and type of stakeholders was organised in July 2019 to present the main outcomes of the work. Proposed recommendations were discussed with the audience. After the workshop, the main recommendations were finalised. The work was based on an iterative approach with feedback from stakeholders. Also, the outcomes of the work are presented in the report.

2.4 Normative references and references to LCA guidelines

The following documents, in whole or in part, are normatively referenced in this document and are indispensable for its application. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies.

● EN ISO 14040:2006, Environmental management - Life cycle assessment - Principles and

framework

● EN ISO 14040:2006, Environmental management - Life cycle assessment - Requirements and

guidelines

● EN ISO 14067:2018, Greenhouse gases - Carbon footprint of products - Requirements and

guidelines for quantification

● European Commission: International Reference Life Cycle Data System (ILCD) Handbook - General

guide for Life Cycle Assessment - Detailed guidance. First edition March 2010. EUR 24708 EN.

Luxembourg. Publications Office of the European Union; 2010

● European Commission: PEFCR Guidance document - Guidance for the development of Product

Environmental Footprint Category Rules (PEFCRs). Version 6.3, May 2018.

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3 Terms and definitions For the purposes of this document, the terms and definitions given in EN ISO 14040:2006, EN ISO 14044:2006 and the following apply.

To simplify the reading of the report, we make use of typical “standardisation language”: The requirements / provisions in this document are marked as either “shall”, “should” or “may” to identify the provisions’ requirement status:

● “shall”: the provision is a mandatory requirement and must always be followed, unless for

specifically named exceptions, if any.

● “should”: the provision must be followed but deviations are permissible only if, for the given

case, they are clearly justified in writing, giving appropriate details. Reasons for deviations can

be that the respective provision or parts of it are not applicable, or if another solution is clearly

more appropriate. If the permissible deviations and justifications are restricted, then these are

identified in the context of the provision.

● “may”: the provision is only a methodological or procedural recommendation. The provision can

be ignored or the issue can be addressed in another way without the need for any justification

or explanation.

NOTE: Instead of "may" the term "recommended" is sometimes used and equivalent.

3.1 Definition of CCU

CCU for Carbon Capture and Utilisation has been defined for the scope of this study as “those technologies that use carbon dioxide (CO2) as a feedstock and convert it into value-added products such as fuels, chemicals or materials.''

Along with CO2, alternative carbon sources and/or energy carriers may be present in feed gases, especially in flue gases, which have been or might be perceived in the wider context of CCU, e.g.,

1. Carbon monoxide, CO (e.g., coking gas, blast furnace gas, converter gas),

2. Methane, CH4 (e.g., coking gas, chemical process off-gases, flare gas, mining gas),

3. Low weight olefins (e.g., ethylene, propylene from chemical process off-gases),

4. Syngas (CO/H2) (e.g., coking gas, blast furnace gas, chemical process off-gases).

In the scope of this work, the carbon source of CCU is restricted to CO2 from process gases and flue gases (fossil or biogenic) or CO2 from the atmosphere. However, the guidelines presented in this work can be applied to other carbon compounds in other off-gases (such as those produced from process emissions in the iron & steel, cement and chemical industries).

3.2 The CCU system

In CCU systems, CO2 is considered as a raw material. The first use of CO2 is the direct use for its physical properties as a solvent or a working fluid (physical properties). This application is one of the main utilisations of CO2 today. CO2 can also be used as a source of carbon, as there are many carbon-containing chemical products that could be synthesised via CCU. Chemical or biological processes can transform CO2 into different products such as synthetic fuels (liquid or gaseous), chemical commodities and chemical building blocks, building materials or food products. Figure 2 below shows examples of the main uses of

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CO2 with or without conversion.

Figure 2: Simple classification of CO2 uses (Source: IEA5)

The range of potential CO2 uses/applications is very large and includes the intermediate use by which the CO2 is not chemically altered and the use of CO2 by conversion into a product. Most of today’s industrial applications are based on the direct use of CO2, such as for greenhouses, carbonated beverages or enhanced oil recovery (EOR). However, the largest demand of CO2 today is for the production of urea (100 Mt of CO2). Figure 3 below illustrates the different options for a CCU system.

Figure 3: Example of key product chain

5 "Putting CO2 to Use - Creating Value from Emissions", IEA, September 2019

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The path leading from CO2 to a given product can be direct (e.g electrochemical conversion of CO2) or indirect (e.g., syngas followed by thermo-chemical conversion), and based on processes of varying efficiency (in technical, environmental or economic terms). All chemical products containing carbon could in principle be synthesized from CO2. The main barrier is the energy required to transform CO2, a very stable molecule, into an energy carrier (as methane). The other route, functionalisation of CO2 may require less energy but require the presence of a co-reactant that has higher intrinsic chemical energy (i.e. less negative Gibbs free energy) to enable the conversion of CO2 at mild conditions6. Examples of co-reactants are epoxies and methane. Products in this category include carboxylates, carbamates, ureas and carbonates.

3.3 Sources of CO2

Figure 4: CO2 sources: from concentrated to diluted CO2

For CCU, the best CO2 sources are those where CO2 is available at high concentrations because of the lower energy penalty of capture. The lower the concentration of CO2, the higher the amount of energy needed for its capture. Several LCA studies have shown that not all CO2 sources are equivalent and the origin of the CO2 therefore influences the results. Table 1 illustrates the wide variety of CO2 sources from industrial processes or combustion. Because of this, the characteristics of the carbon source shall be described within an LCA by the CO2 concentration, the concentration of other gases and compounds, pressure, temperature and any other specific relevant parameters.

CO2 can also be captured from processes using biomass for anaerobic digestion, fermentation (as production of bioethanol), or gasification. In this case, even if the origin of CO2 is biogenic, the environmental footprint of the capture shall be taken into account.

6 Angew, Chem. Int., pp. 187 –190, 2012

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Table 1: Potential sources of CO2 with average cost of capture7

Note: estimated capture rate (%) refers here to the share of the total emissions of the full plant that will be captured by the capture unit

Recently, new developments of capture technologies have demonstrated the ability to capture CO2 from the atmosphere. This is known as Direct Air Capture (DAC). As these technologies are at early stage, the energy required for these processes (and the costs of capture) is considerable with current capture cost estimates in the order of $300-600/t CO2, and estimates for future Nth-of-a-kind costs in the range of $60-250/t CO28. As the current energy consumption of these systems is considerable, they need to be operated with renewable electricity and/or heat in order to avoid net CO2 emissions, i.e. more CO2 being emitted than captured.

7 Naims, H. Environ Sci Pollut Res (2016) 8 ICEF 2018. Direct air capture of carbon dioxide. ICEF roadmap 2018

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4 ISO alignment An LCA for a CCU product shall include the four phases of LCA (Figure 5). General LCA requirements and guidelines are provided in EN ISO 14044:2006. Regarding LCA for CCU, the following areas of special attention are covered in this document:

1. Consideration of co-products

2. Ensuring no double accounting

3. Correct attribution of impacts

4. Awareness of differences between CCU and non-CCU products

5. Origin and source of CO2 and the products derived from this

Figure 5: The four phases of LCA9

4.1 Goal and scope definition

The goal and scope definition is the first phase of any life cycle assessment. The goal defines the purpose of the study, i.e. the research question(s) to be answered, whereas the scope definition describes in detail the object of the LCA study, i.e. the exact product or other system(s) to be analysed.

According to EN ISO 14040 (chapter 5.2.1), the goal states a number of items such as the intended application or the intended audience. Furthermore, “the scope should be sufficiently well defined to ensure that the breadth, depth and detail of the study are compatible and sufficient to address the stated goal.”

For further general requirements (for any LCA study), we refer to chapters 6.2 and 7.2 of this report as

9 ISO 14040

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well as to the ILCD Handbook (chapter 7).

Specific requirements for LCA for CCU studies are dealt with in chapters 6.3 and 7.3 of this report.

4.2 Life Cycle Inventory analysis (LCI)

The inventory analysis (LCI) is the second phase of any life cycle assessment. During this phase, the actual data collection, modelling of the system (e.g. product) and resultant calculations are done. This should be done in line with the goal definition and meeting the requirements derived in the scope definition phase.

According to EN ISO 14040 (chapter 5.3.1), the inventory analysis involves “data collection and calculation procedures to quantify relevant inputs and outputs of a product system.” This includes:

● Data collection,

● Data calculation, and

● Allocation of flows and releases.

For further general requirements (for any LCA study), we also refer to the ILCD Handbook (chapter 7).

Specific requirements for LCA studies for CCU are dealt with in chapters 10 and 11 of this report:

● Overarching data and model aspects are covered in chapter 10, and

● Selected feedstock- and energy-related aspects are covered in chapter 11.

4.3 Life Cycle Impact Assessment (LCIA)

The impact assessment (LCIA) is the third phase of any life cycle assessment. It aims at evaluating the significance of potential environmental impacts using the LCI results.

According to EN ISO 14040 (chapter 5.4.1), the inventory analysis involves “associating inventory data with specific environmental impact categories and category indicators, thereby attempting to understand these impacts.” The LCIA consists of mandatory elements (selection of impact categories, classification and characterisation) and optional elements (normalisation, grouping, weighting).


Specific requirements for LCA studies for CCU regarding the selection of impact categories are treated in chapter 12 of this report.

4.4 Life Cycle interpretation

The interpretation is the fourth and last phase of any life cycle assessment. Here, the findings from the inventory analysis and the impact assessment are appraised in order to answer questions posed in the goal definition.

According to EN ISO 14040 (chapter 5.5), the interpretation “should deliver results that are consistent with the defined goal and scope and which reach conclusions, explain limitations and provide recommendations”.


Specific requirements for LCA studies for CCU regarding uncertainty analysis are treated in chapter 13 of this report.

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5 Goal definition The goal (and scope) definition is the first phase of any life cycle assessment. It defines the purpose and the target audience of the study.

5.1 Goal of the LCA study

According to EN ISO 14044:2006 (chapter 4.2.1), “the goal [...] of an LCA shall be clearly defined and shall be consistent with the intended application.” Essentially, the goal definition describes the research question to be answered. The goal definition is decisive for all the other phases of the LCA. A clear, initial goal definition is hence essential for a correct later interpretation of the results.

5.2 General requirements (for any LCA study)

Although the objective of this report is to address the specificities of LCA for CCU, in this section some general requirements related to the goal definition are described, mainly for the reader’s convenience and reminder.

When defining the goal of the LCA study, the requirements of EN ISO 14040:2006 (chapter 5.2.1.1) and EN ISO 14044:2006 (chapter 4.2.2) shall apply.

In defining the goal of an LCA, the following items shall be unambiguously stated according to EN ISO 14044:2006 (chapter 4.2.2):

1. the intended application of the study;

2. the reasons for carrying out the study (and decision-context; see ILCD Handbook, chapter 5.3);

3. the intended audience, i.e. to whom the results of the study are intended to be communicated;

and

4. whether the results are intended to be used in comparative assertions intended to be disclosed

to the public.

In addition to these four items, two further items shall be identified according to the ILCD Handbook:

5. the limitations of the study: specific limitations of the usability of the LCA results due to the

applied methodology, assumptions made or limited impact-coverage shall be identified and

prominently reported (ILCD Handbook, chapter 5.2.2)

6. the commissioner of the study and other influential actors (ILCD Handbook, chapter 5.2.6).

5.3 Specific requirements for LCA for CCU studies

The proper identification of the so-called decision-context is absolutely crucial for LCA, since it directly determines a number of key aspects in all four phases of the LCA. Therefore, the formal approach to derive the applicable goal situation from the intended application and general decision-context as detailed in the ILCD Handbook (chapter 5.3) shall be followed.

Three different decision-context situations of practical relevance in LCA can be differentiated in Table 2:

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Table 2: Combination of two main aspects of the decision-context: decision orientation and kind of consequences in the background system or other systems. Source: ILCD Handbook

Two examples of these situations are:

1. What is the macroeconomic effect for GHG reduction if the CCU system is established?

→ Meso-/macro-level decision support (Situation B)

2. What is the carbon footprint of the targeted intermediate or product?

→ Micro-level decision support (Situation A) or Accounting (Situation C)

The decision-context of an LCA study for CCU shall be classified as belonging to any of these three archetypal goal situations. These guidelines are intended to cover decision support situations (i.e., situations A or B in Figure 6), therefore accounting as indicated within the ILCD Handbook (situation C) is currently out of scope of the guidelines, as illustrated in Figure 6.

This classification directly determines the LCI modelling principles (attributional and consequential) and the related main LCI method approaches (allocation and system expansion / substitution).

Figure 6: Decision tree to identify the goal of the LCA

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5.4 Summary and key messages

The goal definition describes the research question to be answered. Since the goal definition is decisive for all the other phases of the LCA, a clear initial goal definition is essential for a correct later interpretation of the results.

In addition to the general requirements of EN ISO 14040:2006 and EN ISO 14044:2006, the identification of the so-called decision-context requires particular attention when performing an LCA study for CCU. The decision-context directly determines a number of key aspects in all four phases of the LCA. Therefore, the formal approach to derive the applicable goal situation from the intended application and general decision-context as detailed in the ILCD Handbook shall be followed.

The present guidelines are intended to cover “decision support” situations (i.e., situations A or B in Figure 6), therefore “accounting” - as indicated within the ILCD Handbook (situation C) - is out of scope of the present guidelines.

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6 Scope definition The scope definition is the second part of the first phase of any life cycle assessment. It defines what to analyse and how.

6.1 Scope of the LCA study

According to EN ISO 14044:2006 (chapter 4.2.1), “the [...] scope of an LCA shall be clearly defined and shall be consistent with the intended application.” Essentially, the scope definition describes the object of the LCA study (i.e. the exact product or other system(s) to be analysed) in detail. This shall be done in line with the goal definition (see chapter 4 of this report).

6.2 General requirements (for any LCA study)

Although the objective of this report is to address the specificities of LCA for CCU, in this section some general requirements related to the scope definition are described, mainly for the reader’s convenience and reminder.

According to EN ISO 14040:2006 (chapter 5.2.1.1), “the scope of the LCA study should be sufficiently well defined to ensure that the breadth, depth and detail of the study are compatible and sufficient to address the stated goal.” Due to the iterative nature of LCA, the scope may have to be revised due to unforeseen limitations, constraints or as a result of additional information. Such modifications, together with their justification, shall be documented.

In defining the scope of an LCA, all items listed in EN ISO 14044:2006 (chapter 4.2.3.1) shall be considered and clearly described. These include, among others, the following ones:

● Product system to be studied;

● Function(s) and functional unit

● System boundary

● Allocation procedures

● LCIA methodology and types of impacts

● Assumptions

● Limitations

Furthermore, we refer to the ILCD Handbook (chapter 6).

Product system to be studied

Based on the initial information on the process(es) or system(s) to be studied given in the goal definition, details often need to be added in the scope definition. It is recommended to provide a detailed description of the system to be studied, including technical drawings, flow charts and/or photos (adapted from ILCD Handbook, chapter 6.4). This system specification closely interrelates with the system(s)’s function(s), its functional unit(s), and its reference flow(s) which are addressed below.

Function, functional unit and reference flow

In defining the functional unit, the requirements of EN ISO 14040:2006 (chapter 5.2.2) and EN ISO 14044:2006 (chapter 4.2.3.2) shall apply. More details can be found in the ILCD Handbook (chapter 6.4) and in the PEF CR Guidance (version 6.3, May 2018).

The scope of an LCA shall clearly specify the functions (performance characteristics) of the product system

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being studied. The elements of the functional unit include: 1. The function(s) / service(s) provided: “what”

2. The extent of the function / service: “how much”

3. The expected level of quality: “how well”

4. The duration / lifetime of the product: “how long”

The functional unit shall be consistent with the goal and scope of the study. One of the primary purposes of a functional unit is to provide a reference to which the input and output data are related. Therefore the functional unit shall be clearly defined and measurable.

An appropriate reference flow shall be determined in relation to the functional unit. The quantitative input and output data collected in support of the analysis shall be calculated in relation to this flow.

System boundaries

In defining the system boundary, the requirements of EN ISO 14040:2006 (chapter 5.2.3) and EN ISO 14044:2006 (chapter 4.2.3.3) shall apply.

The system boundary shall be explained clearly and in an unambiguous way, preferably in a technical flow chart. The exclusion of any life cycle stages shall be documented and explained.

Allocation procedures / Approaches for solving multifunctionality

Regarding the choice between different LCI method approaches for solving multifunctionality, we refer to the ISO hierarchy, as detailed in EN ISO 14044:2006 (chapter 4.3.4). This is especially relevant in the LCI phase, see chapter 11.2.

LCIA methodology and types of impacts

It shall be determined which impact categories, category indicators and characterization models are included within the LCA study. The selection of impact categories, category indicators and characterization models used in the LCIA methodology shall be consistent with the goal of the study and considered as described in EN ISO 14044:2006 (chapter 4.4.2.2).

6.3 Specific requirements for LCA for CCU studies

Specific requirements for LCA studies for CCU are listed under the following subchapters. In addition, the limitations, assumptions and methods to assess issues specific to CCU products should be explained.

6.3.1 Product system to be studied

These specific requirements are “outsourced” to chapter 8 of this report.

6.3.2 Function, functional unit and reference flow

Given the wide range of possible CCU products and their functions as well as different goal and scope definitions, it is neither useful nor possible to define a common functional unit. It is important that all functions of the product system are adequately captured, i.e. the service(s) delivered by a CCU-based product should be the basis for defining the functional unit.

First of all, it has to be determined whether the CCU process delivers a product (energy carrier/fuel, chemical, material) or an energy storage service or both.

For energy carriers such as transportation fuels, energy content (e.g. 1 MJLHV) has been used extensively as the functional unit, making it some sort of “de-facto standard” over time. However, using an energy service (e.g. 1 vehicle km using a specified means of transport) would be more appropriate to reflect

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differences in fuel conversion efficiencies. The latter is especially important for CCU fuels whose chemical structure and composition can differ from their conventional counterparts (reference product) or for comparison to electromobility (where the energy content of the fuel doesn’t make sense). Therefore, we recommend that in the case of CCU fuels for transportation, 1 vehicle km (or 1 tonne km) using a specified means of transport should be chosen as the functional unit – irrespective of whether their chemical structure and composition is identical to or different from the conventional counterpart.

The same considerations apply to other energy carriers used for heating/cooling. Although also here, energy content (e.g. 1 MJheat) is used very often, we recommend defining a FU related to the provided energy service, e.g. MJ useful heat. In the case of using energy content for industrial heat (steam), the temperature and pressure of the steam shall be reported.

In the case the CCU product (chemical or material) and the conventional counterpart (reference product) are chemically and mechanically identical, a mass-based functional unit (e.g. 1 kg of product) should be used. In the case of different chemical structure and composition, a specific functional unit should be defined based on equal technical performance.

In case of products with multiple uses, separate functional units (as well as conventional counterparts / reference products) should be defined and separate LCA calculations should be performed. Organic carbamates, for example, can be used as insecticides, chemical industry inputs and for pharmaceutical uses.

If the CCU process delivers an energy storage service, a functional unit quantifying the storage characteristics should be defined. If, however, the CCU process delivers an energy storage service along with a product, a functional unit quantifying the storage characteristics should be defined together with the functional unit of the product.

Last but not least, for the comparison of various CCU processes, 1 kg of CO2 input should be used as the functional unit. All emission losses through incomplete conversion and through reactions shall be accounted for, to illustrate various CO2 conversion losses.

The following Table 3 summarises the recommended functional units.

Table 3: Recommended functional units (FUs)

Recommended FU

Product: Energy carrier - Transportation fuel 1 vehicle km (or 1 tonne km) using a specified means of transport

Product: Energy carrier - Other Define FU quantifying the energy service

Product: Chemical/material - chemically identical 1 kg of product

Product: Chemical/material - chemically different Define FU based on equal technical performance

Energy storage system Define FU quantifying the storage characteristics

Comparison of various CCU processes 1 kg of CO2 input

6.3.3 System boundaries

Cradle-to-grave should be the default system boundary to assess the environmental impact of a CCU technology (see Figure 7). This means that any technical input to establish and manage the system producing CO2 should be considered within the system boundary and thus be part of the LCA of the CCU product. Likewise, the use phase and end-of-life treatment (which ultimately re-releases the CO2) should

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be considered within the system boundary. Another key parameter is energy and that specific impacts of energy used shall be calculated instead of using average values (e.g., land use from additional renewable power generation and additional transmission grid capacity needed (if this is the case). Only in this way, meaningful conclusions regarding carbon neutrality / negativity can be drawn in an unrestricted form.

However, other systems boundaries may be chosen, but in this case, justification shall be provided. An obvious exception is CO2 obtained by direct air capture (DAC): in this case, it is not necessary to consider the primary CO2 emitter (see Figure 8). Here, a gate-to-grave system boundary is recommended which includes the CO2 capture process.

Figure 7: System boundary for fossil and biogenic CO2: cradle-to-grave

Figure 8: System boundary for CO2 from direct air capture (DAC): gate-to-grave

We discourage the use of a cradle-to-gate system boundary, even for products (energy carriers/fuels, chemicals, materials) with identical chemical structure and composition. The reason is that the CCU product might not just substitute today’s average application of its conventional counterpart but a very specific application of this chemical intermediate. A typical example is the production of a CO2-based chemical (e.g., formic acid) which will aim to have a different application (i.e. service) in the future and therefore will have different end-of-life emissions than today (e.g., in the case of formic acid if in the

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future it is intended to be used as a hydrogen carrier or a chemical intermediate instead of today’s use as a preservative and antibacterial). Also, in the case of transportation fuels, non-CO2 emissions from fuel combustion (e.g. particulate matter, SO2 and NOX) might differ quite considerably between CCU fuels and conventional fuels such as fossil gasoline or diesel.

The use of a gate-to-gate system boundary is strongly discouraged for three reasons:

1. The assumption that identical chemical structure equals identical downstream emissions (and

therefore in a comparative study one could omit those) is only valid if the two products provide

identical services. In many CCU cases, chemical compounds are intended to be produced from

CO2 for different services than today’s (e.g., as energy carriers, new chemical building blocks, etc).

In such cases, disregarding changes in the services and in the end-of-life emissions will result in

wrong conclusions.

2. Carbon neutrality and or negativity can only be claimed if the CO2 emissions in the upstream, the

use phase and end of life are correctly considered. For a detailed discussion on this please see

Tanzer & Ramirez.10

3. There is currently no standardised easily accessible LCI data on “CO2” and more specifically on CO2

capture technologies, thus there is no standardised data which would enable the upstream

impacts to be calculated through a standard database such as Ecoinvent.

6.3.4 Allocation procedures / Approaches for solving multifunctionality

Regarding the choice between different LCI method approaches for solving multifunctionality, we refer to the ISO hierarchy, as detailed in EN ISO 14044:2006 (chapter 4.3.4). The choice of LCI method approach depends on the goal of the LCA for CCU study. Although the ISO hierarchy aims at avoiding allocation wherever possible (and to apply a system expansion approach), there are indeed certain circumstances which require determination of one product’s environmental performance. In this case, a basket-of-products approach, which is for example highly recommendable for policy information at systems comparison level, is not helpful. In such cases, allocation can be appropriate and shall be justified. Moreover, the CO2 burden needs to be divided between the primary CO2 emitter and the CCU plant. This topic is addressed in detail in chapter 11.2.

6.3.5 LCIA methodology and types of impacts

Specific requirements are treated in chapter 12 of this report.

6.4 Summary and key messages

The scope definition defines what to analyse and how. In addition to the general requirements of EN ISO 14040:2006 and EN ISO 14044:2006, a number of specific requirements for LCA studies for CCU are formulated. These are mainly related to functional unit and system boundaries.

As regards the functional unit, we conclude that - given the wide range of possible CCU products and their functions as well as different goal and scope definitions - it is neither useful nor possible to define one common functional unit for LCA studies for CCU. It is important that all functions of the product system are adequately captured, i.e. the service(s) delivered by a CCU-based product should be the basis for defining the functional unit. It has to be determined whether the CCU process delivers a product (energy

10 Tanzer S., Ramirez A (2019). When are negative emissions negative emissions? Energy and Environmental

Science, DOI: 10.1039/c8ee03338b

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carrier/fuel, chemical, material) or an energy storage service or both. Based on this, we recommend functional units for a number of cases (see Table 3).

Regarding the system boundary, the present guidelines require that “cradle-to-grave” should be the default system boundary to assess the environmental impact of a CCU technology. Only in this way, meaningful conclusions regarding carbon neutrality / negativity can be drawn in an unrestricted form. Other system boundaries are discouraged (“cradle-to-gate”) or even strongly discouraged (“gate-to-gate”), however, they may be chosen on the condition that a justification is provided. An obvious exception from the “cradle-to-grave” rule is CO2 obtained by direct air capture (DAC): in this case, a “gate-to-grave” system boundary is recommended which includes the CO2 capture process.

In the present guidelines, further important elements of the scope definition are “outsourced” to other chapters, e.g. the description of the product system to be studied (chapter 8), allocation procedures (chapter 11.2) and LCIA methodology and types of impacts (chapter 12). The reader is referred to those chapters as well.

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7 Description of CCU system

7.1 Introduction

In the scope definition, there are general requirements for any LCA.

The requirements of EN ISO 14040:2006, 5.2.1.2, 5.2.2, 5.2.3, 5.2.4 and EN ISO 14044:2006, 4.2.3 shall apply.

In defining the scope of an LCA, all items listed in EN ISO 14044:2006 (chapter 4.2.3.1) shall be considered and clearly described. See chapter 7.2.

This chapter gives CCU-specific recommendations for the description of a product system to be studied with the following aspects:

● Main processes of CCU systems: what is the product? ● Key information and parameters of the main processes ● CO2 sources ● Carbon flows to/from the atmosphere and CO2 pool in the atmosphere ● Comparison to the reference system ● Summary - key messages

7.2 Main Processes

The CCU system shall be described, covering the following six main processes in the whole life cycle as shown in Figure 9:

1. Source of CO2 2. CO2 capture and, when needed, compression 3. CO2 purification and transport when needed 4. CO2 conversion process (incl. demand and source of electricity/hydrogen as auxiliary

material/energy input) 5. H2 production 6. Distribution of products 7. Use and application of products 8. End of life/Recycling

If the “CO2 capture” and the “CO2 conversion process” are at the same place, they might be summarized as “CCU plant”. Ideally, they should not be combined so that the contribution of the CO2 capture process can be reported separately in the assessment results (allowing for the comparison against direct air capture or other CO2 sources)

The “CO2 source” describes where the carbon or CO2 is taken from and whether it is from biogenic, fossil or atmospheric origin.

The “CO2 capture” describes the technology that is used to capture the CO2 from the CO2 source to make it available for the CCU system at the required specifications. If the capture unit produces CO2 at general specifications (for instance, those required for CO2 transport only) and the specifications are different from those required for the CCU unit, additional purification units should be explicitly specified. The units can be allocated to either the CO2 capture or to the CO2 conversion processes depending on the location where the purification takes place.

The “CO2 conversion process” describes the technology that is used to produce the products from the carbon obtained by using energy e.g. electricity or hydrogen. It should contain all units required to

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produce the required product specifications for the market envisioned.

The “Distribution of products” describes how the products are distributed to the place where they are used.

The “Use and application of products” describes the use or application of the products and the service that is provided by them e.g. transportation, packaging.

The “End of life/Recycling” describes what happens with the products after their use or application, e.g. recycling to new products or use for energy generation.

Figure 9: Main processes of the CCU system

7.3 Key information and parameters of main processes

The following specification for each of these main processes shall be described in detail: 1. Products: main characteristics, use/application, possible co-products 2. Current and expected state of Technology (TRL 1- 9) 3. Location/country 4. Time: today/future 5. Scale of system: e.g. as t/h, t/a, MW, TWh/a 6. Technical characteristics: full load hours, optionally characteristics of dynamic operation,

efficiencies, aux. energy and material demand, direct emissions/losses of CO2, emissions of other substances to air and water, wastes, etc.

7. Scheme of mass and energy flows between different processes 8. Quantified annual Mass and Energy balance incl. CO2 balance 9. Various other details: e.g. pure CO2 use in research project

For these main processes, the technical data describing the mass and energy balance shall be documented. The mass and energy balance should be on an annual basis giving also the full load hours. If intermittent electricity/energy sources are used (e.g. wind or solar) an hourly resolution over the whole

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year shall be provided showing how the electricity demand matches with the demand of the CCU system based on real data or modelled operation characteristics. If intermittent electricity/energy sources are used (e.g. wind or solar) characteristics of the load profile of the CCU plant shall be explained in such a way and level of detail that the claimed full load hours are comprehensible (e.g., x hours at 100 % load, y hours at 50 % load, z hours at 0 % load, including for example in addition number and dynamics of load changes). In addition, mass and energy balance shall be provided for at least the main reference loads (e.g., 100 %, 50 % and 0 %). Lastly, it shall be described which real volatile electricity generation or provision profile the claimed operation of the CCU plant is related to.

So, in the inventory analyses the ● inputs of mass and energy and ● outputs of products and residues

shall be given for each of the 6 main processes of the CCU system.

It is important to note that the energy and mass balances change if the CCU plant is operated not at constant load but for example along with power rate provided by a volatile source such as wind or solar power. Various options for flexible operation exist (e.g., load adjustment of single units or of the whole CCU plant, change in heat integration such as partial or no heat integration, intermediate storage of electricity and/or feedstock, intermediates, products). If a CCU system is designed and operated flexibly in along with the available fluctuating electricity, this shall be described. If a system is to be operated flexibly, it needs to be visible in the design and data selection. An example is given in Figure 10. The example illustrates two CCU designs for the direct electrochemical conversion of CO2 to ethylene. One of the designs operates at full load and one is designed to follow an intermittent load. In the latter case, two design options are possible, building storage capacity as part of the design (not in the figure) or designing the system in a flexible way that allows for ramping up and down. An example of such a design is shown in Figure 10, where the flexibility is obtained at the expense of heat integration. In other words, heat integration is decreased in order to allow a more flexible system. The energy and mass profiles of both systems are therefore different and will affect the LCI.

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Figure 10: Example for continuous and flexible operation: Electrochemical conversion of CO2 to ethylene a) continuous (from grid); b) intermittent from dedicated wind power11

7.4 CO2 sources

Most important is the source of carbon dioxide. The following options exist: ● CO2 from combustion (fossil, biogenic, waste12) ● CO2 from gasification (fossil, biogenic, waste) ● CO2 from fermentation (alcohol fermentation: ethanol; anaerobic digestion: biogas) ● CO2 from biogas upgrading to biomethane ● CO2 from chemical processes (steel, cement, etc.) ● CO2 from the atmosphere ● CO2 from coal & oil & gas extraction, e.g. flaring of exhaust gases, CO2 as a by-product of oil/gas

extraction ● CO2 from any other source, e.g. geothermal energy use

For a CCU system, the most attractive CO2 sources (from an economic point of view) are the concentrated ones, this is because the energy consumption for the capture and purification of these concentrated sources are lower than the capture of CO2 from diluted flue gases or from the atmosphere.

11 Ege B (2019). Electrochemical conversion of CO2 into ethylene. Master thesis, Faculty of Applied Sciences and

Faculty of Technology, Policy and Management, TU Delft.

12 which is a mixture of fossil and biogenic carbon, which has to be specified in the system description

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Other C1 sources such as carbon monoxide (CO) could also be interesting to use and are currently attracting attention.

The most relevant characteristics of the CO2 sources are and shall be described: ● CO2 concentration: vol-% ● Temperature (T) and pressure (p) ● Concentrations of other gases, e.g. CO, H2, H2O, N2, NOX, SO2 ● Concentration of other relevant impurities e.g, trace metals

● Annual flow: t or Nm³ per year

The further specification of the CO2 source shall include ● Primary products/services of the origin of the CO2 source

o Energy carrier, e.g. steam, electricity, fuel o Material production, e.g. steel, cement o None, e.g. air

● Origin of CO2 o Fossil fuel o Biogenic/biomass o Waste (mixture of fossil & biogenic carbon) o Atmospheric

7.5 Carbon flows to/from atmosphere and CO2 pool in atmosphere

As the effects of CCU systems on global warming are very relevant, the carbon flows and pools affected by CCU System shall be described. So, the CO2 flows from and to the atmosphere related to the CCU system are relevant as well as the atmospheric CO2 pool.

In Figure 11 the scheme of carbon flows and atmospheric CO2 pool affected by a CCU system is shown, where the source of the additional CO2 that is an input in the CCU system is relevant. The main aspect is the additional amount of CO2 in the atmosphere and how much additional fossil carbon is flowing from underground into the atmospheric CO2 pool.

Figure 12 illustrates the CO2 in the atmosphere which is affected by different types of carbon, pools and flows. For a proper carbon balance, four different pools of carbon shall be considered:

1. Fossil carbon stored in fossil resources 2. Biogenic carbon stored in biogenic resources, above or below ground 3. Aquatic carbon stored in water and, 4. Atmospheric carbon stored in the atmosphere.

Between these pools carbon flows. The effect of the CCU system on these carbon flows and the change of the atmospheric pool shall be described in the system boundaries and the results. The carbon flows and pools are time dependent and are strongly depending on the lifetime of the products.

Depending on the technology, CCU will lock up CO2 in the product for varying time periods, While fuels or chemicals like urea only lasts for a very short period of time before the carbon is re-released, other products such as building materials could last hundreds of years, while biodegradable plastics containing a proportion of materials from CCU may degrade over a ten-year basis. The lifetime of the products is relevant to be reflected in the interpretation of the results e.g. end of life management options and the CO2 balance, this is covered more within Chapter [12].

In the following, two illustrative examples are given – one for a CCU system producing a material and the second for a CCU system producing a transportation fuel.

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Figure 11: Scheme of Carbon flows and atmospheric CO2 pool affected by the CCU System

Figure 12: CO2 in atmosphere affected by different types of Carbon, pools and flows

In Figure 13, the first example of a CCU system producing a material and its CO2 flows is shown. CO2 is taken from the atmosphere as a CO2 source for the CCU system. The energy and material for the CCU system to produce the material uses (partly) fossil energy, so the supply of the auxiliaries causes a CO2 flow to the atmosphere from fossil resources. The CCU plant fixes atmospheric CO2 so that, in net terms, no additional CO2 flow from the use phase occurs. At the end of life phase the material, for instance, a non-biodegradable plastic, can be landfilled, where the stored atmospheric CO2 is fixed underground. When this is not an attractive future option, the material is combusted to produce energy and the atmospheric CO2 in the product flows back to the atmosphere or the material is recycled to new products which in turn requires energy and raw materials . So, in total, the net effect on the CO2 pool in the atmosphere is increased by the flow of fossil carbon from the supply of the auxiliaries over the total

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lifetime of the material produced from the CCU system.

In Figure 14 a second example of a CCU System producing a fuel and its CO2 flows is shown. CO2 is taken from the combustion of fossil fuel, which produces an energy service, e.g. heat, for the CCU system. The energy and material for the CCU system to produce the material uses (partly) fossil energy, so the supply of the auxiliaries causes a CO2 flow to the atmosphere from fossil resources. Then the fuel from the CCU plant - fixing the fossil CO2 - is used to supply an energy service, e.g. transportation. As a combustion process takes place the fossil CO2 in the product flows to the atmosphere. So, in total, the net effect on the CO2 pool in the atmosphere is increased by the flow of fossil carbon from the supply of the auxiliaries for the CCU plant and the fossil CO2 from the fossil resource. However, two energy services are provided, both directly by the use of fossil fuel and indirectly by the fuel produced in the CCU plant.

Figure 13: Example 1: CCU System (material) & CO2 flows

Figure 14: Example 2: CCU System (Fuel) & CO2 flows

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7.6 Comparison to reference system

The environmental effects of the products or services from the CCU system shall be compared to the effects of conventional or other new products and services, which is called “Reference system”. Therefore, in the comparison, the reference system and the CCU system shall have the same services.

The reference system shall be described in similar detail as the CCU system by focusing on the following issues:

● Provide same services/products ● State of Technology (TRL 1-9) ● Country/region/integration in infrastructure ● Scale/capacity e.g. kt/a ● (main) Resources (energy and mass) ● Main processes.

But beside the processes to provide the reference products and services the reference system without CCU shall also deal with the following topics

● Depending on the goal and scope of the LCA, relevant alternative “direct” use of renewable resources used for the CCU plant needs to be considered in the reference case: e.g. it has to be specified if additional renewable electricity is produced for the CCU plant or if renewable electricity is bought on the market or through power purchase agreements.13 (This is discussed in greater detail in Chapter 11).

● Current use of heating value of the C-source, e.g. current combustion of a flue gas containing CO, H2 to generate electricity and or heat and which may not be available anymore if the flue gas is used for CCU.

● Use of “waste heat” from the reference system in the CCU system, where waste heat is defined as heat that is not used in the reference system. A more detailed discussion on this point is provided in chapter 11 of this report.

● Plausible conditions for the reference systems. For instance, unless dealing with very specific case studies, if the LCA study is conducted for the current situation, then a description of the state of technology of the reference system, e.g. Best Available Technology (BAT) for the reference system is required. If the CCU system will be deployed in the future, it should be taken into account that the reference/competing technology will also develop in the same timeline. Therefore conventional technologies may be replaced by future ones (also in the reference scenario). For example, future technologies with low CO2 emissions, e.g. direct reduction process instead of blast furnace technology in steel making, electrolytic hydrogen instead of steam reforming or steam reforming with advanced CCS.

In the comparison, the CCU system and the reference system shall provide the same services, mostly energy and products, which might be supplied by the

● CCU system ● CO2 source ● alternative use of renewable resources and ● use of the heating value of e.g. CO and H2 from C source

13 The issues of alternative direct use of renewable resources will be analyzed in more detail in future work and

further conclusions and recommendations will be drawn adfn discussed.

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7.7 Summary - key messages

The key messages of the system description are summarized in the following: ● Proper description of CCU systems: products/services ● Describe main processes (e.g. TRL) and their linkages, CO2 capture shall be included and described

in detail ● Key information/parameters of main processes ● Special focus on CO2 source, electricity and hydrogen (further details in chapter 11) ● Proper annual mass and energy balance, consider changes in balances in case of flexible operation ● CO2 pool in atmosphere and CO2 flows to/from the atmosphere from the CCU system ● Proper description of reference system with the same products/services as for the CCU system

including the alternative use of renewable resources and use of the heating value of e.g. CO and H2 from C-source

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8 Data a

guidelines for life cycle assessment of carbon capture and utilisation · 2020. 5. 7. ·...

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